The field of the invention is concentric pipe joints. Specifically, the invention relates to an annular restraint that minimizes axial movement (separation or compression) of two pipes concentrically joined.
The axially aligned joinder of two pipes is commonly effected by arranging for an enlargement in the diameter of one pipe near its terminal end, so that the other pipe can be partially inserted within it. Once the pipes are joined, it is frequently desired that there be minimal axial movement of one pipe relative to another so as to ensure the integrity of the link.
Securing concentric pipe joints for large waterworks-related piping has proven itself to be a daunting task. On occasion, concrete thrust blocks have been poured in and around changes in piping direction to transfer thrust forces to the surrounding soil. Although the method has been used for years, it is often impractical because of pipe congestion, soil conditions, cost considerations, effects upon future excavations, or time constraints.
Restraint devices have been developed and installed external to the concentric pipe joint. Some of these devices feature an external restraint ring connected to each pipe near the joint, the restraint rings themselves being subsequently interconnected to secure the joint. These mechanisms are field adaptable; however, as pipe diameters increase, the designs become heavy and cumbersome. Furthermore, the restraint components are directly exposed to the elements, which, over time, erodes their performance.
Finally, some restraints have been literally designed into the pipes themselves. These restraints frequently feature complex geometries that must be molded into the terminal end portions of the pipes to facilitate joinder. These designs do feature reduced weight; however, the terminal end portions are frequently either difficult to make, complicated to install/disassemble, or cost ineffective. Obviously, field adaptations and modifications to these restraints are difficult as well. Some systems incorporate the restraint into the design of the sealing gasket; however, these systems aren""t generally available for pipes in large sizes, and some designs make it almost impossible to disassemble this type of joint.
This patent describes and claims several preferred embodiments of a novel pipe joint restraint. The restraint is specifically designed to resist axial movement of an inner spigot pipe relative to an outer socket pipe with which it has been joined. The restraint conveniently operates in the annular region between the two pipes (defined more precisely hereinbelow).
The restraint generally comprises a spigot wedge ring, a socket wedge ring, and one or more specially designed wedge housings. The spigot wedge ring comprises one or more spigot gripping protrusions which, upon contact, frictionally engage the spigot pipe. The socket wedge ring similarly comprises one or more socket gripping protrusions which, upon contact, frictionally engage the socket pipe. The wedge housings position the spigot wedge ring and/or the socket wedge ring so that the gripping protrusions grip the pipes, preventing axial movement (whether separation or compression).
Highly effective wedge ring designs are disclosed. The wedge rings described generally feature at least one frusto-conical surface which engages an opposed frusto-conical surface on either another wedge ring or a housing resulting in a more effective engagement of the gripping protrusions upon the pipe walls. In fact, in many of the embodiments disclosed herein, the greater the force inciting the undesired axial movement of the pipes, the greater the force that will be applied by the gripping protrusions to the pipe walls to halt the movement.